A vacuum evaporation installation, which is used in the production of semiconductors by molecular beam epitaxy, for example, generally comprises a main enclosure or growth module connected to pumping means (primary and secondary pumps) and containing the substrates to be treated, as well as one or more effusion sources containing the material or materials to be evaporated. These control modules and sources are maintained at ultra-high vacuum during deposition processes, which vacuum pumping takes a significant period of time to accomplish.
Effusion sources are typically removable and exchangeable for changing deposition processes and also for refilling or recharging purposes. A source typically includes a crucible with a select compound, referred to as an evaporation cell, which is heated to cause the compound to evaporate from the evaporation cell for deposition to a substrate. In order to permit the recharging of these sources with various materials and without breaking the ultra-high vacuum of the growth module, installations have been developed in which the evaporation cell to be recharged is detachable and is connected to the main enclosure by a metal bellows. When the bellows is compressed, the cell is in the normal evaporation position in the growth module, and then when the bellows is stretched or extended, the cell is retracted out of the growth module into a small auxiliary chamber. This chamber can be separated from the growth module by the action of a ultra-high vacuum valve. Such an installation makes it possible to recharge the cell while only placing the auxiliary chamber under atmosphere again and without breaking the vacuum of the growth module.
Although satisfactory from certain respects, such installations suffer from disadvantages due to the very significant travel which has to be given to the bellows (typically more than 500 mm), which can lead to high costs, due both to the cost of the bellows and that of the guidance and translation system, which must be very accurate to ensure a correct alignment over a considerable distance, along with a risk of pollution of the enclosure by the effect of degassing operations of the long bellows. The bellows are made of thin metal convolutions that can be damaged by physical contact during normal use. In addition, when the sources are mounted in an upward looking direction, debris (e.g., particles/flakes) can drop down onto the source, which can damage the bellows. Both issues can lead to expensive and time-consuming bellows replacement. Also, a bellows support system must overcome the force created by the difference in pressure between the vacuum inside the chamber and the atmospheric pressure outside the chamber. A pressure of approximately 14.7 psi is applied to every square inch of a bellows when the vacuum system is pumped down. For a 2 inch diameter deposition source the bellows effective area needs to be approximately 5.0 square inches. Multiply that by the 14.7 pounds per square inch of atmospheric pressure and a force of 73.5 pounds needs to be applied to hold the bellows system from moving. This constant force needs to be overcome by any support system of a metal bellows containing apparatus. This disadvantage is eliminated by the present invention. Installations that include a bellows also typically have large overall dimensions, which is prejudicial to access to the other evaporation sources. Thus, there is a need to provide deposition sources, systems, and methods that include retractable sources that overcome fundamental limitations and drawbacks of presently available systems.